Its a Strategic Game where Fleets tussle for control of Whole Systems, its not a ground level Grunt fights Grunt game.... do the latter on largest size map for every Planet you take, and it will take a Huge amount of time to complete the game.
GalCiv is fought at a Strategic Level, its not about Tactical Combat. There is some of the letter for sure, Fleet battles Fleet etc etc. However to open up ground level fighting in the same manner, is to mix Tactical Warfare with the whole Strategic picture. It also opens up the game to the need for a different type of software and control mechanism.
I don't mean to suggest that I want a Total War kind of planetary battle-- but certainly something other than "launch spores or nukes" and then watch some numbers count down to see who wins.
I'd also like to see more thought put into the populations of planets used for troop invasions. It's rather absurd that I can bring a transport ship that I just loaded with a few thousand people from a colonized planet and then, 2 turns later, invade another planet with them. There should be some cost for training and/or a cost associated with maintaining an effective ground-based fighting force, depending on what level and equipment you want to field in your civilization.
This was what I missed from, I think it was MOO, or perhaps another 4X space game-- you actually had to develop ground-based fighting technology as part of the tech tree (weapons, tanks, etc) and then physically purchase/build them, move them with transports, and then use them as an invasion force. GalCiv glosses over this entire aspect, which is an immense logistical undertaking.